Measurement of Higher-Order Mode Losses in SPEAR II by Shift in Synchrotron Phase and Increase in Net Cavity Power.

摘要

It has been estimated that the loss to higher-order cavity modes in SPEAR II will be 135 keV per cavity at 100 mA for a 10-cm bunch (sigma/sub z/ = 5 cm). This corresponds to a loss of 10 MeV for a 50-m PEP structure. The power lost to higher modes in each SPEAR II cavity at 100 mA would be 13.5 kW. A loss of this order can be measured by calorimetry. This loss is also large enough to cause a significant increase in the net rf power input into the cavities over the power input with no higher-mode excitation. In addition, the higher-mode loss can also produce a measurable shift in the synchronous phase angle. Numbers for these effects are computed in this paper.